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Friction launch control system for a vehicleRelated Patent Categories: Interrelated Power Delivery Controls, Including Engine Control, Clutch Control, Regulated Clutch EngagementFriction launch control system for a vehicle description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20060205563, Friction launch control system for a vehicle. Brief Patent Description - Full Patent Description - Patent Application Claims
FIELD OF THE INVENTION [0001] The present invention relates to a vehicle powertrain, and more particularly to a launch control system for a vehicle powertrain. BACKGROUND OF THE INVENTION [0002] A vehicle powertrain typically includes a transmission, an engine, and a powertrain controller. The transmission transfers engine output torque through a gear reduction to a driveshaft, which rotates the wheels of the vehicle. The powertrain controller controls the operation of the transmission and the engine. Powertrains traditionally include launch devices including, but not limited to, a torque converter or friction clutch. More specifically, automatic transmissions generally include a torque converter and manual or automated manual transmissions (AMTs) include a friction clutch. Friction launch devices gradually couple rotating members so that they become fixed for rotation together. [0003] Traditional friction launch control strategies include closed loop slip speed control and fluid coupling emulation control. Closed loop slip speed control monitors the slip speed across the friction launch device and regulates the slip speed so that is follows a single, desired profile. Closed loop slip speed control is not sufficiently robust against system variations and can not maintain stable operation. Fluid coupling emulation control simulates fluid coupling characteristics and regulates the friction launch device to emulate a single torque absorption curve. Fluid coupling emulation control, however, does not provide sufficient degrees of freedom to achieve a desired engine stall speed for a variety of throttle openings. SUMMARY OF THE INVENTION [0004] Accordingly, the present invention provides a launch control system for a vehicle having an engine. The launch control system includes a clutch that selectively enables torque transfer from the engine and a control module that determines a launch torque based on a throttle position and an engine speed to achieve a target engine stall speed. The control module determines a clutch torque based on the launch torque and regulates engagement of the clutch based on the clutch torque. [0005] In other features, the launch torque is determined based on an initial launch torque and a modifier. The initial launch torque is determined based on the throttle position and the engine speed. The modifier is determined based on a speed ratio between an input shaft and an output shaft of the transmission and the throttle position. [0006] In other features, the clutch torque is further determined based on a lock torque. The lock torque is determined based on an engine torque. [0007] In other features, the clutch torque is determined based on a lock-up variable. The lock-up variable is based on a lock-up state of the clutch and has a value that ranges from 0 to 1. The lock-up variable is determined based on a throttle position and a speed of the output shaft. [0008] Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. BRIEF DESCRIPTION OF THE DRAWINGS [0009] The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein: [0010] FIG. 1 is a schematic illustration of a vehicle incorporating the launch control system of the present invention; [0011] FIG. 2 is a schematic illustration of the vehicle of FIG. 1 including an exemplary transmission; [0012] FIG. 3 is a signal flow diagram illustrating calculation of a clutch launch torque according to the present invention; [0013] FIG. 4 is a graph illustrating an exemplary look-up table for determining a friction launch torque; [0014] FIG. 5 is a graph illustrating an exemplary look-up table for determining a friction launch torque; [0015] FIG. 6 is a graph illustrating an exemplary look-up table for determining a modifier term; [0016] FIG. 7 is a graph illustrating an exemplary look-up table for determining lock-up and unlock speeds; [0017] FIG. 8 is a state transition diagram for determining a launch clutch state; and [0018] FIG. 9 is a graph illustrating resultant friction launch characteristics using the launch control system of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [0019] The following description of the preferred embodiments is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. For purposes of clarity, the same reference numbers will be used in the drawings to identify similar elements. As used herein, the term module refers to an application specific integrated circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or group) and memory that execute one or more software or firmware programs, a combinational logic circuit, or other suitable components that provide the described functionality. Continue reading about Friction launch control system for a vehicle... 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